Design of a reflection-suppressed all-optical diode based on asymmetric L-shaped nonlinear photonic crystal cavity

A simple design method for suppressing the reflection of the all-optical diode based on the L-shaped photonic crystal (PC) cavity is proposed. Analyzing the linear resonant characteristics of the PC cavity and using the nonlinear coupled-mode theory, the strategy for obtaining reflection-suppressed structure is illustrated. Based on the design rule, a “reflection-suppressed all-optical diode” is presented, and numerical solutions indicate that the designed structure has a small reflection as well as an extremely large nonreciprocal transmission ratio

A rigorous definition of nonlinear parameter γ and effective area A_eff for photonic crystal optical waveguides

A rigorous definition of nonlinear parameter γ for high-index-contrast (HIC) periodic optical waveguides, such as photonic crystal (PC) optical waveguides, is proposed. The definition is fully vectorial, and approximations assumed in previous works are unnecessary. The γ values calculated by the proposed definition are compared with those obtained by previous definitions, the rigorous nonlinear mode solver, and measured values for weakly guiding optical fibers, HIC Si-nanowire waveguides, and PC waveguides. It is demonstrated that the γ values calculated by proposed definition agree well with those of the rigorous nonlinear mode solver and experiments for all three waveguides, showing the validity of the definition

PLC-Based LP11 Mode Rotator With Curved Trench Structure Devised From Wavefront Matching Method

A compact and low-loss PLC-based mode rotator is proposed. The mode rotator with the curved trench structure is designed based on the wavefront matching method, which is an optimization algorithm based on the beam propagation method. The proposed mode rotator is 45% in size (1 mm) and has lower loss (1/5) compared with the conventional structure that has a straight trench. Furthermore, the proposed mode rotator can achieve low-mode crosstalk

Heralded creation of photonic qudits from parametric down-conversion using linear optics

We propose an experimental scheme to generate, in a heralded fashion, arbitrary quantum superpositions of two-mode optical states with a fixed total photon number n based on weakly squeezed two-mode squeezed state resources (obtained via weak parametric down-conversion), linear optics, and photon detection. Arbitrary d-level (qudit) states can be created this way where d = n + 1. Furthermore, we experimentally demonstrate our scheme for n = 2. The resulting qutrit states are characterized via optical homodyne tomography. We also discuss possible extensions to more than two modes concluding that, in general, our approach ceases to work in this case. For illustration and with regards to possible applications, we explicitly calculate a few examples such as NOON states and logical qubit states for quantum error correction. In particular, our approach enables one to construct bosonic qubit error-correction codes against amplitude damping (photon loss) with a typical suppression of root n - 1 losses and spanned by two logical codewords that each correspond to an n-photon superposition for two bosonic modes